AA Atlas question...

[Loud3 10+ year member]

for those of you that have them... what imp. does each coil show, to be exact?

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[Pyro_By_Nature 5,000+ posts]

They are a SVC sub.The gold terminals were not meant to be powered, although the nominal impedence of the coil that's not supposed to be powered is 2 ohms iirc.

 

[Loud3 10+ year member]

Haha. Interesting.

I am reading 1.3 ohm (on the 2 ohm) and 2.8 ohm(on the 4 ohm)

Damaged, or just real world coil? I know the American Bass DX is a single 4 ohm driver, but IRL, the coils are 2.7 ohm

Help?

 

[squeak9798 5,000+ posts]

You are measuring the DCR of the coil with the DMM, not the impedance. Two totally different things.

DCR is constant. Impedance fluxuates with frequency, enclosure, etc...which is why it's called a "nominal" (or average) impedance. It's the "average" load the subwoofer will present to the amplifier over it's bandwidth.

 

[Loud3 10+ year member]

Explain. DMM adjusted to the omega symbol, with the positive lead into omega/V, and the negative lead into COM.

 

[squeak9798 5,000+ posts]

Explain. DMM adjusted to the omega symbol, with the positive lead into omega/V, and the negative lead into COM.

Yes, and that measues the DC Resistance (DCR) of the coil, not the nominal impedance.

Resistance is the opposition to the flow of direct current (DC), and this figure remains constant. This is what you are measuring with your DMM. The resistance of the coil (in a T/S parameter this is referred to as either Re or DCR).

Impedance is the opposition to the flow of alternating current (AC)....alternating current of course is what music consists of. Impedance is not constant and will vary with different variables such as frequency. Ever look at an impedance graph for a speaker? Those show you what the impedance of the speaker is doing over the bandwidth of frequencies. And the speaker's nominal impedance (shown in T/S parameters as Z or Znom) is sort of like an average of what load the speaker will present to the amplifier over it's operating range. A speaker may have a rated impedance of 4ohms, but it may only actually present a 4ohm load to the amplifier at a few frequencies...the rest of the time the actual impedance is higher or lower because it varies with frequency.

The DCR will almost always be lower than the nominal impedance the speaker is rated for.

 

[squeak9798 5,000+ posts]

And because a speaker has a DCR of, say 3.4ohms, that does not mean that it's "really" a 3.4ohm speaker. It's still a nominal 4ohm speaker ...meaning "on average" it will present around a 4ohm load to the amplifier.

 

[Loud3 10+ year member]

And because a speaker has a DCR of, say 3.4ohms, that does not mean that it's "really" a 3.4ohm speaker. It's still a nominal 4ohm speaker ...meaning "on average" it will present around a 4ohm load to the amplifier.

I figured as much, but never seen a 'dcr' of that low compared to imp. Usually I see a closer comparison of the two. Like a 3.8 to a 4 ohm coil...

I stand corrected!

Thanks Squeak.

 

[johnson 10+ year member]

My IDMAX D2 measures around 3 ohms when wired in series. Blow on the cone a little bit and you will see the numbers change.